class Solution {
public:
    int dx[4] = { 0, 0, 1, -1 };
    int dy[4] = { 1, -1, 0, 0 };
    vector<vector<int>> highestPeak(vector<vector<int>>& isWater) {
        int m = isWater.size(), n = isWater[0].size();
        queue<pair<int, int>> q;
        vector<vector<int>> h(m, vector<int>(n, -1));

        for (int i = 0; i < m; i++)
            for (int j = 0; j < n; j++)
                if (isWater[i][j] == 1) {
                    h[i][j] = 0;
                    q.push({ i,j });
                }

        while (q.size())
        {
            int sz = q.size();
            while (sz--)
            {
                auto [a, b] = q.front();
                q.pop();
                for (int i = 0; i < 4; i++)
                {
                    int x = a + dx[i], y = b + dy[i];
                    if (x >= 0 && x < m && y >= 0 && y < n && h[x][y] == -1)
                    {
                        h[x][y] = h[a][b] + 1;
                        q.push({ x,y });
                    }
                }
            }
        }
        return h;
    }
};